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arXiv 0710.0629astro-ph
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旋转磁化中子星的三种盘振荡模

Three Disk Oscillation Modes of Rotating Magnetized Neutron Stars

R. V. E. Lovelace, M. M. Romanova

摘要:

本文讨论了旋转磁化中子星周围吸积盘的三种特殊模式,这三种模式可以解释低质量X射线双星中出现的千赫兹准周期振荡(QPO)的分离现象。这些模式的存在要求吸积物质的角速度有一个最大值,并且流体在这个最大值附近处于稳定的、接近圆形的运动,而不是快速地向恒星移动或离开盘平面进入漏斗流。目前还不知道这些条件是否会发生,但我们正在探索这与三维磁流体动力学模拟,并将报告的结果在其他地方。第一种模式是一个共转模式,它是径向捕获在附近的最大磁盘旋转速率和不稳定。第二种模式,相对缓慢旋转的恒星,是一个磁驱动偏心($m=1$)振荡的磁盘在Lindblad半径附近的磁盘旋转的最大值激发。第三种模式,有关快速旋转的恒星,是一个磁耦合偏心($m=1$)和轴对称($m=0$)径向磁盘扰动,其中有一个内部Lindblad半径也在附近的最大磁盘旋转。我们认为,第一个模式与较高的QPO频率,$ν_u$,第二个与较低的QPO频率,$ν_\ell =ν_u-ν_*$,第三个与较低的QPO频率,$ν_\ell=ν_u-ν_*/2$,其中$ν_*$是恒星的旋转速率。

英文摘要:

We discuss three specific modes of accretion disks around rotating magnetized neutron stars which may explain the separations of the kilo Hertz quasi periodic oscillations (QPO) seen in low mass X-ray binaries. The existence of these modes requires that there be a maximum in the angular velocity of the accreting material, and that the fluid is in stable, nearly circular motion near this maximum rather than moving rapidly towards the star or out of the disk plane into funnel flows. It is presently not known if these conditions occur, but we are exploring this with 3D magnetohydrodynamic simulations and will report the results elsewhere. The first mode is a corotation mode which is radially trapped in the vicinity of the maximum of the disk rotation rate and is unstable. The second mode, relevant to relatively slowly rotating stars, is a magnetically driven eccentric ($m=1$) oscillation of the disk excited at a Lindblad radius in the vicinity of the maximum of the disk rotation. The third mode, relevant to rapidly rotating stars, is a magnetically coupled eccentric ($m=1$) and an axisymmetric ($m=0$) radial disk perturbation which has an inner Lindblad radius also in the vicinity of the maximum of the disk rotation. We suggest that the first mode is associated with the upper QPO frequency, $ν_u$, the second with the lower QPO frequency, $ν_\ell =ν_u-ν_*$, and the third with the lower QPO frequency, $ν_\ell=ν_u-ν_*/2$, where $ν_*$ is the star's rotation rate.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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